1. Field of the Invention
The present invention relates to a brake for bicycles and more particularly to a coaster brake mounted on the rear wheel shaft of a bicycle for stopping the bicycle with the reverse rotation of the pedal.
2. Prior Art
Existing coaster brakes, which are mounted on the shaft of a bicycle rear wheel, include a male screw cylinder rotated by means of a pedal, and a screw cone having a tapered outer surface. The screw cone is screwed to the male screw cylinder to adapt an axial motion of the screw cone. Thus the screw cone presses the brake shoe, which is divided into two sections, to widen it so that the brake is stuck fast to the inner surface of the hub body, thereby putting the braking action into effect.
Nevertheless, when the screw cone to axially moved is not given fractional resistance, the screw cone is likely to skid together with the male screw cylinder resulting in no braking action.
In order to prevent such skidding of the screw cone, for example, Japanese Utility Model Application Provisional Publication No. SHO 56-35433 discloses various kinds of devices in which a clutch spring is fitted into the brake cone so that the clutch spring partially contacts the screw cone. Since all of the conventional brakes have a clutch spring slidably in contact with the internal surface of the cylindrical screw cone so that the resultant resistance unavoidably has a narrow limit, sliding is easily caused; however, the screw cone may still sometimes skid. In particular, when the brake is used for a long time it causes wear and deformation, increasing the possibility of skidding.